Electrical transformer



June 27, 1967 v. B. HONSINGER 3,328,735

ELECTRICAL TRANSFORMER 7 Filed March 15, 1966 n /M M v QERMPM @1Q4pM wW 2;; W5 Km /@llfkpkmg I United States Patent ()1 3,328,735 ELECTRICAL TRANSFORMER Vernon B. Honsinger, Cincinnati, Ohio, assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis. Filed Mar. 15, 1965, Ser. No. 439,762 4 Claims. (Cl. 336-120) This invention relates to transformers and more specifically to a rotatable transformer in which the secondary winding of the transformer can be rotated and is adapted to be connected to a rotating load.

Rotat-able transformers are used for the purpose of transferring electric current and power from a stationary member to a rotating member. Hence, rotating transformers are used as exciters to provide electrical energy to the field of an AC generator, to provide electrical power to illuminate a rotating structure such as a carrousel or to heat a rotating member suchas a screw type conveyer used in certain chemical processes.

There are various methods of transferring electrical power from a stationary member to a rotating member such as a conventional exciter and contacts between a stationary and rotating member. However, both of these devices have drawbacks which restrict their use. For example, in the conventional exciter there is a magnetic fl'ux linkage between the rotating and stationary members and the frequency of the voltage on the rotating member is dependent on the speed of the rotor and relative motion between the two members and, hence, is subject to con siderable fluctuation. In the second method mentioned, current is transmitted between a rotating member such as a commutator or slip ring and a stationary member such as a carbon brush. In this system there is very little power loss and the frequency of the voltage of the transfer power is not dependent on the speed of relative motion. However, there is always a certain amount of sparking between the stationary and movable parts as well as a certain amount of wear and carbon dust formed. Hence, this type of structure is completely unacceptable under certain conditions such as an explosive atmosphere or in places where strict requirements are in effect as far as dust and the like are concerned. Hence, the use of sliding contacts are unacceptable in many industries such as the chemical and petrochemical industries.

The rotating transformers of the prior art are usually made of solid cores or annular laminations of iron. However, both of these cores provided a very high reluctance path for the magnetic flux. In order to obtain the current and voltage required for industrial use of these transformers, excessive heat was generated which in turn decreased the flux carrying capacity of the cores and rendered the transformers unacceptable.

The transformer of this invention overcomes the problems mentioned above by providing a magnetic core in which the individual laminations extend generally in a direction to provide a low reluctance path around the coils of the transformer. To accomplish this the iron laminations of the core are positioned so that the fiat portion of the laminations extend generally parallel to the direction of the flux rather than transverse to it.

Therefore, it is the object of this invention to provide a new and improved transformer.

Another object of this invention is to provide a new and improved rotatable transformer.

Another object of this invention is to provide a new and improved core structure for a rotating transformer.

3,328,735 Patented June 27, 1967 Other objects and advantages will be apparent from the following description when read in connection with the accompanying drawing, in which:

FIG. 1 is an exploded perspective view of a rotatable core of a rotating transformer of this invention;

FIG. 2 is a cross section view of a motor driven unit utilizing the transformer of this invention to provide current to a rotating heating element;

FIG. 3 illustrates an alternate embodiment of a rotating core for a transformer of this invention using a spirally wound coil, and

FIG. 4 is another embodiment of this invention showing a solid core with a portion cut that is used as both core and coil.

Referring more particularly to the drawings by characters of reference, the invention is illustrated in FIGS. 1 and 2 in connection with a rotatable transformer 10 having a core 11 made up of a rotating member 12 and a stationary member 13. In the unit illustrated in FIG. 2, the rotating member is driven by an electric motor. Appropriate primary and secondary coils 14 and 15, respectively, are wound in the core between the members 12 and 13. The primary coil 14 which is stationary is connected to a suitable source of alternating current. The secondary coil 15 rotates with rotating core member 12 and is connected to a load such as the illustrated screw 16 of a conveyer 17 for moving and mixing materials. The conveyer has a tank 18 with two inlets 19, 19a and a discharge 20.

The stationary core member 13 can be of any suitable construction such as illustrated and described in copending United States patent application, Ser. No. 377,822 filed June 24, 1964. The laminations of the core are arranged to form an annular member and each lamination is positioned in a plane that includes the center line of the core. The leg portions of each lamination extend radially inward toward the center line of the core. The connecting portions of each the U-shaped laminations extend longitudinally parallel to the axis of the core.

The rotating member 12 of the illustrated core 11 is constructed of two axially spaced sets 22, 22a of annular laminations and a plurality of arcuately spaced laminations 23 that lie in a plane that includes the center line of the core. These laminations 23 are arranged in side by side relation to form an annular member 24 that extends between the sets 22, 22a of annular laminations. The annular laminations lie in a plane perpendicular to the axis of the core and the laminations 23.

The sets 22, 22a and the annular member 24 combine to form therebetween a torus 27 for housing the secondary windings or coil 15 of the transformer. A similar torus may be formed in the stationary core member. As illustrated in the drawing, the torus is rectangular in cross section and when viewed in a plane including the center line of the core'it presents a rectangular winding window.

Of course, the specific configuration of the winding win- For ideal transformer operation, each lamination should form a continuous uninterrupted path around the coils, and adjacent laminations should lie in substantially parallel planes to provide a magnetic path of minimum reluctance. In a rotating transformer it is impossible to provide these ideal conditions, but in the rotating transformer of this invention the laminations of the rotating core are arranged around the center line of the core in such a manner that the flat surface of each lamination lies in a plane that is substantially parallel to that portion of the flux path immediately adjacent the lamination. For example, the laminations in sets 22 and 22a extend radially outward in the direction of the flux around the coil in these areas. The laminations 23 extend axially along the shaft 31 which is the direction of the flux around the coil in that area. Hence, this preferred flux path is formed around the coil in such a manner that it flows parallel to the flat portions of the laminations at all places except the junction between the laminations 23 and the sets of laminations 22, 22a. Because of this preferred arrangement of the laminations providing a low reluctance flux path, there is a minimum amount of eddy current formed in the core. Correspondingly, there is a minimum amount of heat generated which is extremely important in the rotating transformer structure because in the prior art transformers the amount of heat generated was a serious drawback to its commercial adoption.

As might be expected, the assembly of laminations 23 that make up the central member 24 of the core is not a simple matter. However, one satisfactory method of assembling these laminations is to affix the individual laminations at one end to a flexible member such as a strip of adhesive material and then wrap the strip of material with laminations adhering thereto around a mandrel or the like to form an annular member. The laminations can then be clamped by appropriate means to hold the laminations in a rigid position until the sets 22, 22a are positioned on either end of the member 24 to form a rigid annular core 12.

In an alternate embodiment of this invention as illustrated in FIG. 3, a rotating core 35 is made up of two sets of annular end laminations 40 and 42, similar to the sets of end laminations in the embodiment of FIG. 1. However, between these laminations is a spirally wound member 43. This member is made up of alternate layers of sheets of magnetic material 44 and electric conducting material 45. It may be desirable in some applications to place a layer of electric insulating material 46 between the conductor 45 and the magnetic material 44. The layers of magnetic material combine with the end laminations to form a low reluctance path for the flux around the coil in the same manner as the laminations in the first embodiment. In this embodiment the entire space between the end laminations can be filled by the spirally wound members because no additional space is required to form a torus or winding space for the coil.

A third embodiment is shown in FIG. 4 in which a solid annular core 50 has a V-shaped section 51 removed. The core is made of a magnetic material that is also an electric conductor so as to perform the functions of both the core and the coil of the transformer. An appropriate pair of connectors 52, 53 are provided with the core 50 to connect the coil to an appropriate load.

Although three embodiments of this invention have been illustrated and described, it will be apparent to those skilled in the art that various modifications and changes can be made therein without departing from the spirit of the invention or from the scope of the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A rotatable member for an electric transformer comprising:

two sets of annular iron laminations mounted on a shaft and being axially spaced from each other;

a first sheet of magnetic material and a second sheet of electric conducting material wound in the form of a helix and positioned between said sets, said first sheet providing a magnetic flux linkage between said sets of laminations;

electrical insulation positioned between said sheets,

and lead wires connected to said second sheet to conduct electric current to said second sheet and thereby form a coil of said rotating member.

2. An electric transformer comprising:

an annular core having a coil mounted therein, a second core mounted for rotation within the bore of said first core, said second core comprising a sheet of electric conducting material and a sheet of magnetic material wound in the form of a helix,

electrical insulating material positioned between said sheets,

and lead wire connected to said electric conducting sheet to form the coil for said second core.

3. An electric transformer comprising:

an annular magnetic stationary member having a coil formed therein,

a generally solid cylindrical member composed of a single material having the characteristics of both electric and magnetic conductivity rotatably mounted within the bore of said stationary member,

said cylindrical member being positioned to form a substantially closed low reluctance magnetic circuit with said stationary member,

means for connecting said cylindrical member to an electric circuit to form a coil for said member.

4. An electric transformer comprising:

an annular magnetic core having an electric coil mounted therein;

a second magnetic core mounted for rotation within the bore of said first core, said second core comprising two sets of annular iron laminations mounted on a shaft and being axially spaced from each other; and a plurality of radially disposed laminations positioned between said sets, each of said radial laminations lying in a plane that includes the center line of said shaft and extending radially outward between said sets to a point inward of the periphery of said sets,

and electric windings positioned in said torus.

References Cited UNITED STATES PATENTS 1,394,901 10/1921 Hobart 336--l20 X 2,053,176 9/1936 Bouwers 336234 X 2,498,702 2/1950 Naharn 336-234 X 2,641,682 6/1953 McKenna 336 177 X 2,716,736 8/1955 Rex 336-177 X 2,878,425 3/1959 Kudoh 336-83 X 2,997,567 8/1961 Connelly 336234 X LEWIS H. MYERS, Primary Examiner.

L. 'E. ASKIN, Examiner.

D. J. BADER, T. J. KOZMA, Assistant Examiner. 

1. A ROTATABLE MEMBER FOR AN ELECTRIC TRANSFORMER COMPRISING: TWO SETS OF ANNULAR IRON LAMINATIONS MOUNTED ON A SHAFT AND BEING AXIALLY SPACED FROM EACH OTHER; A FIRST SHEET OF MAGNETIC MATERIAL AND A SECOND SHEET OF ELECTRIC CONDUCTING MATERIAL WOUND IN THE FORM OF A HELIX AND POSITIONED BETWEEN SAID SETS, SAID FIRST SHEET PROVIDING A MAGNETIC FLUX LINKAGE BETWEEN SAID SETS OF LAMINATIONS; 